Various valve configurations of the type commonly referred to as gate valves have been devised. A common configuration is of the general type disclosed in U.S. Pat. No. 3,420,499 issued Jan. 7, 1969 to Plepcher et al. In that design a hand operated handle is rotated to raise and lower a valve member contained in a valve housing. As shown, a round plug is commonly employed as the gate valve member. The round plug, which may be formed of rubber of another elastomer, is expanded by action of shoulders engaging the top of the plug. A common shortcoming of such configurations is caused by the fact that the rubber plug on expanding due to pressure from a washer or shoulder does not consistently expand in the areas where sealing is needed when pressure is applied.
A further problem is that the bottom of the valve contains a depression in which liquids can accumulate. While minor amounts of such accumulation is no problem in many applications, it is not acceptable in piping used to convey foodstuffs. Such standing accumulations would be highly undesirable because it would represent an area where foodstuffs could accumulate and decay and in which bacteria could multiply. Thus, such depressions in foodstuff conveying lines are prohibited both by government and industry standards.
Another valve configuration which has been proposed involves the fitting of a barrel-shaped plug or valve member into a conically shaped recess. See, for example, U.S. Pat. No. 4,592,534 issued Jun. 3, 1985 to Ueda et al. The barrel shaped plug in such configurations, however, is free to expand on compression into the passageway through the valve and is thus subject to excessive wear upon repeated opening and closing of the valve.
It is an important object of the present invention to provide an improved valve assembly of the gate valve type in which the valve element is raised and lowered in a valve chamber. Both the valve chamber and the plunger are preferably of an elliptical or oblong shape with the wide dimension extending perpendicularly to the passageway through the valve. The valve member is formed of a soft rubber element generally shaped to engage the bottom of the valve chamber and is caused to expand when the member engages the bottom of the chamber by means of an internal tapered member within the outer rubber member. The interior element which is preferably formed of metal is of a shape which causes the rubber element to expand so that the valve chamber is tightly sealed.
It is a further object to provide such a valve which can be tightly sealed even in the absence of any recess or depression in the bottom of the valve chamber. A related further object relates to the fact that the absence of such recess makes the present valve configuration ideal for use in fluid food conveying systems. The fluid foods may be liquids, viscous materials, semi-solids or liquids containing suspended solids.
An important attribute of the valves of the present invention is that materials are prevented, by the design, from entering the valve stem region behind the valve plug. A further aspect of the invention relates to the provision of wash ports above the valve body, thereby providing aseptic valves when needed. A further advantage of the invention is that the valve plug cannot rotate within the valve cylinder because of its non-circular cross-section.
Briefly summarized, the objects and advantages of this invention are achieved by providing a gate valve assembly which includes a valve body having a fluid passage extending laterally therethrough. The passage has an inlet end and an outlet end, with means at the inlet end and at the outlet end to connect the valve body to a fluid conveying conduit. The passage has a bottom surface coplanar with the bottom of the conduit and is free of recesses capable of preventing the drainage of liquids. An axially extending valve chamber intersects the passage and is disposed perpendicularly to the axis of the passage, the chamber having an elliptical cross-section with its widest dimension perpendicular to the passage. An axially and non-rotationally movable valve member is fitted closely within the chamber and has an internal, downwardly tapered hard, core member formed of metal, glass, ceramic or hard plastic material. The core is surrounded by an elastomeric elliptically cross-sectioned outer member. The elastomeric member has a generally flattened bottom surface adapted to engage the bottom of the passage and is dimensioned to close the passage when extended into the closed position. Means, which may be motor driven or hand operated, are provided to extend and retract the valve member within the valve chamber.